1. Field of the Invention
This invention relates generally to a stainless steel wire, and more specifically to a type of stainless steel wire having a nickel plated layer on the outer surface of the stainless steel wire.
2. Description of the Prior Art
Various types of stainless steel wire of superior anticorrosive nature are known, and these are widely employed in the production of coiled springs.
However, when the stainless steel wire is formed into coiled springs, some difficulties in the coiling process are experienced. The most fundamental of these difficulties is the frictional seizure or galling caused between the stainless steel wire and the feed rollers, the wire guide, and the bending die of an automatic coiling machine. If such frictional seizure occurs, irregularities in the dimensions or in the structure of the coiled springs inevitably result, and the operation of the coiled springs thus produced are not constant. Furthermore, wear in the feed rollers and bending die is severe, rendering the production of the coiled springs utterly unsuccessful.
In order to avoid such difficulties, a stainless wire plated with lead or coated with a suitable resin has been employed in automatic coiling machines.
However, where a stainless steel wire plated with lead is employed, there is always a hazard from pulverized lead, which is poisonous to te human body, being spread around the coiling cite. Furthermore, both the lead plated and the resin covered stainless steel wire easily change in color during the stress relieving process (at about 400.degree. C) carried out after the coiling process, rendering the coiled springs esthetically unpleasant, and requiring another process for removing the lead or resin layer before the stress-relieving process.
Therefore, the primary object of the present invention is to provide a stainless steel wire so processed that the above described drawbacks of conventional stainless steel wires can be essentially eliminated.
Another object of the present invention is to provide a stainless steel wire which possesses sufficient lubrication when it is processed in a coiling machine.
Still another object of the present invention is to provide a stainless steel wire which preserves its aesthetically pleasant features even after it is subjected to a stress-relieving process following the coiling process.
An additional object of the invention is to provide a stainless steel wire which also preserves its anti-corrosive nature after it is subjected to the stress-relieving and coiling processes.